Carcasses of pneumatic green tires are built as a series of layers of flexible high modulus cords encased in a low modulus rubber. An innerliner is positioned to form the innermost surface of the tire. The green tire is cured in a curing press using a curing bladder, which forces expansion of the tire. During curing, the innerliner expands with the carcass, which is forced against the indentations in the curing mold to form the tread of the tire, and all components are co-cured so as to provide a substantially cohesive bond between one and another.
The innerliner for a pneumatic tubeless tire is typically formed from a compound containing a high proportion by weight of a halobutyl rubber due to its good barrier properties. Before the tire is cured, the entire inner surface of the innerliner and/or the outer surface of the curing bladder are coated with a release agent. The release agent is commonly referred to as a “lining cement” when used on the surface of the innerliner, and as a “bladder lube” or “bladder spray” when used on the curing bladder. The release agent facilitates removal of the curing bladder from the innerliner after curing so that the innerliner is not damaged. The innerliner (or squeege) for a pneumatic tube-type tire is typically a thin layer of ply coat stock to protect the tube from direct contact with nylon. These innerliners normally do not contain halobutyl rubber since barrier properties are not required.
Tires are often required to have a rubbery component bonded to a portion of the tire's innermost surface, i.e., the innerliner. For example, some tires are dynamically balanced by adhering a laminar pad of rubbery material, referred to as a “balance pad”, symmetrically about the circumferential center line of the interior surface of the cured tire. In another example, smart tires include an electronic monitoring device secured to the innermost surface of the tire. The electronic monitoring device is used to record the operating history of a tire, including temperature and pressure, distance traveled, impact sustained, and other data, to transmit the data to the driver or to a designated receiving station, and to do so without taking the tire out of service. A requirement of these components is that they be securely mounted within the tire so as to tolerate any condition to which the tire is subjected without being dislodged. Thus, a strong bond to the innerliner is essential for these components.
Prior to bonding a component, such as a balance pad or electronic monitoring device, to the cured innerliner, the innerliner must be cleaned to remove contaminants present on the innerliner surface from the molding operation. In particular, the release agent must be removed from the innerliner surface. Solvents have typically been used for this cleaning operation. Solvents effective for removing the release agents contain hazardous air pollutants. These solvents are thus subject to environmental regulations, which have become more stringent in the recent past. It would thus be desirable to eliminate the need for solvent cleaning of the innerliner surface in order to comply with strict environmental regulations. In addition, solvent cleaning is labor intensive and costly due to its hazardous nature, such that significant cost savings may be realized by elimination of the solvent cleaning process.
One solution for eliminating the solvent cleaning process is disclosed in commonly-owned U.S. Patent Application Publication No. 2004/0103967. A barrier film is removably adhered to the innerliner surface to protect that surface from contamination by the release agent. While the protective barrier initially sticks well to the green innerliner, it has a tendency to separate or shift during the high pressure lining cement spray and/or during shaping by the curing bladder, and thus, may not completely prevent contamination of the innerliner surface. For example, the lining cement may spray underneath the splice of overlapped film, causing the film to come off. There is thus a need to improve the reliability of protective barriers for the innerliner surface such that these barriers can effectively replace the solvent cleaning process.